Cell division controls final fruit size in three apple (Malus x domestica) cultivars

Abstract

Apple (Malus x domestica) fruit size is dependent on cell division and cell expansion, processes which are subsequently regulated by plant hormones such as auxins, gibberellins, and cytokinins. In this study, we investigated the role of cell division and cell expansion in apple growth and identified which of the two was more deterministic to final fruit size. Three cultivars of different sizes were selected, namely, ‘Twenty Ounce’ (large-sized), ‘Royal Gala’ (medium-sized), and ‘Crabapple’ (small-sized). Gene expression and cell size analyses were conducted over the course of two consecutive seasons. The expression patterns of three classes of genes were markedly similar across all cultivars. Two cell division markers, namely, MdCDKB2;2 and MdANT2, were discovered to be correlatively expressed as both displayed initially high expression levels, which gradually declined from the early to late stages of growth time course. For cell expansion markers, MdEXP3 was upregulated as the cells expanded, while MdARF106 was expressed in both the cell division and expansion stages. Meanwhile, the ripening related gene MdACO1 was expectedly expressed only during the ending stages associated with ripening. Interestingly, the cell measurements taken regularly from each cultivar throughout the same eperimental timespan showed that cell sizes were unaltered and remained constant from initial pollination at the zeroth Days After Pollination (DAP), to ripening at 120 Days After Full Bloom (DAFB).

Genetic variations in MdSAUR36 participate in the negative regulation of mesocarp cell division and fruit size in Malus species

“…It has been reported that both cell division and expansion rates determine the number and size of mesocarp cells and thus the size of ripe fruit in apple. However, cell division was once proposed key to the differences in fruit size among cultivars, because the cell areas of each cultivar, 'Twenty Ounce' (large-sized), 'Royal Gala' (medium-sized), and crab apple (small-sized), were similar at pollination or at ripening (Karim, 2015;Karim et al, 2022). By using an interspeci c hybrid population, we con rmed that no considerable differences were found in mesocarp cell size between large-fruit and small-fruit groups but mesocarp cell number of large-fruit group was signi cantly higher than that of small-fruit group (Figure 2a, 2b).…”

Deciphering the Plant Hormones Cross-Talk during Fruit Development: A Review

“…For fruit set to take place, pollination and fertilisation must be accomplished or the flowers will be abscised [13,15,16]. Pollination is the crucial starting point in fruit development as it is required for fertilisation.…”

“…Pollination is the crucial starting point in fruit development as it is required for fertilisation. During fruit set, rapid cell division occurs and then stops when the fruit reaches its mature size [16][17][18]. Levels of plant hormones, such as auxins, CKs (CKs), and gibberellic acids (GAs), increase to promote fruit set [13,16].…”

“…During fruit set, rapid cell division occurs and then stops when the fruit reaches its mature size [16][17][18]. Levels of plant hormones, such as auxins, CKs (CKs), and gibberellic acids (GAs), increase to promote fruit set [13,16]. In tomato, after successful fertilisation, ovary development into a fruit starts with cell division until roughly 10-14 days, and during the following six to seven weeks, the fruit grows by cell expansion [14].…”